A new study that included almost 1,100 patients found that those whose cancer was spotted by colonoscopy tended to have an earlier stage of disease at the time of their diagnosis, as well as better survival.

In contrast, patients whose colorectal cancer was not diagnosed through colonoscopy were at higher risk of having more invasive tumors, as well as cancers that had already spread to other areas of the body.

The findings provide "yet another compelling reason for asymptomatic, average-risk individuals over the age of 50 to get screened by colonoscopy," said Dr. David Carr-Locke, chief of the division of digestive diseases at Beth Israel Medical Center in New York City. Carr-Locke was not involved in the study.

The findings were published online June 19 in the journal JAMA Surgery.

In the study, researchers led by Ramzi Amri, of Massachusetts General Hospital and Harvard Medical School in Boston, looked at outcomes for nearly 1,100 patients treated for colon cancer. In 217 cases, the cancer had been spotted in a screening colonoscopy.

At the time of their diagnosis, patients whose cancers had not been spotted via colonoscopy had nearly double the odds of having an invasive tumor compared to those whose tumor had been found through a colonoscopy. They also had more than three times the odds for a metastatic tumor that had spread to other parts of the body, the researchers reported.

During follow-up, patients not diagnosed through colonoscopy screening had higher death rates, higher cancer recurrence rates, shorter survival and shorter lengths of time during which they were cancer-free, the team found.

"Compliance to screening colonoscopy guidelines can play an important role in prolonging longevity, improving quality of life, and reducing health care costs through early detection of colon cancer," Amri and colleagues wrote.

Since they were introduced in 2000, colonoscopy guidelines recommended by the U.S. National Institutes of Health appear to have decreased overall rates of colorectal cancer, the researchers said.

Dr. Maurice Cerulli, program director in the division of gastroenterology, hepatology and nutrition at North Shore-LIJ Health System in New Hyde Park, N.Y., agreed that the adoption of routine colonoscopy has "resulted in a decrease in the number of people dying from colon cancer over the past decade."